in all honesty i think you're fine the only reason people flush is for salt buildup from the nutes apparently it makes it taste better i dont know ive always used bud candy and final finish together with good results and really stardawg tasting buds
yea what height are your light at? for seedlings i do 20 inches then 25 after the first 2 weeks then 30 for veg and raise em up for flowering depending on how much the plants stretch.
1st why would u feed seedlings 2nd you dont need that much light unless you got like 20 seedlings i do about 6 seedlings per 130w then bump em up to 300w for veg and then to 450w for flower all my lights put about 900 par at 20 inches perfect for seedlings