Hi!
Please take your piggies off any fresh food until the poos have firmed up properly for 24 hours.
Here is our information on how to best deal with/how soon to see a vet with digestive problems, including soft poos and diarrhea:
Digestive Disorders: Diarrhea - Bloat - GI Stasis (No Gut Movement) And Not Eating
The mainstay of any guinea pig diet (over 80% of what they eat in a day) should be unlimited hay. The more they eat, the better for their gut microbiome, their dental health (it is the highly abrasive silica in hay and grass which keeps the crucial back teeth ground down and which their very fast growth has evolved against) and an improved life span - it can really make the difference between living to the lower end/coming up to the lower end or the higher end and beyond the average life span of 5-7 years.
See veg (including fresh herbs/forage and - very sparingly - fruit) and pellets more in the way of a daily treat than the main meal of the day; veg should make only 10-15% of what a piggy eats and 1 tablespoon of pellets just 5%. Overfeeding pellets, which are full of empty fillers impacts massively on hay consumption, is rather like feeding cake instead of wholewheat bread all the time. Pellets are also high in calcium, so overfeeding can in the long term contribute to bladder stones.
You also want to aim at a balanced mainly leafy mixed veg/herb diet with some high vitamin C ingredients and a wide range of nutritients. Zucchini (UK: courgettes) are not the most of nutritious of veg but they are very watery - hence the soft poos.
Please take the time to read our comprehensive diet, which looks at all food groups from water, hay, pellets, fresh food (with a sample diet picture) and treats in practical detail. You should find it very helpful!
Long Term Balanced General And Special Needs Guinea Pig Diets
The diet guide is part of our much wider new owners guide collection, which specifically addresses all the various issues that we get the most questions and concerns about from new owners in a practical and easy to follow way. It ranges from double-checking the gender upon arrival (mis-sexing is sadly very common); settling in and making friends with your piggies (including a spot of piggy whispering); understanding their behaviour and how their prey animal instincts works; boar and sow information; housing, diet and daily care; safe enrichment and dangerous accessories and toys; learning what is normal and not and when to see a vet.
The guide format allows us to constantly update our information. Here is the link:
Getting Started - New Owners' Most Helpful Guides
Please start saving up for vet care on a weekly/monthly basis as part of the regular maintenance cost and talk about this issue now with any legal guardians or the person who runs the household you live in if you are a minor or still dependent. Guinea pigs are too small and can go downhill too quickly to have the leisure to wait for days in a severe illness or emergency. The right to be free from any discomfort, pain and suffering is one of the five basic animal rights - and there is nothing as upsetting as seeing any pet in your care suffer and die from an entirely curable disease. There is also nothing like the rift it can cause a family.