HELP! All 3 plants getting yellow leaves

Hey guys i need help to diagnosis the problem with my 3 clones. They are budding about 2-3 weeks maybe and they are starting to yellow (not just bottom leaves) and im trying to determine why, I fed it 1/4cup of big bloom fox farm (it says first time use 1/2 cup so i halfed that) and watering every 3 days and used bat guano earthworm castings and a few feedings of grow big back in veg. any ideas?

Im using distilled water 6-6.5ph also

I was told it was Phosphorous deficiency