well my first question I suppose is this. sis the horse manure fully composted. yoiu said composting versed compsted LOL! big difference. ands the lime added will not hurt your seedlings at all man. good for em at lower levels for seedlings. I would use a small bit of seedling mix for that or make your own and add more the the main mix personally but it'll be fine. when using less depeding on waterr and various things PH will always have to be considered throuout your grow. so more is always a good idea than thee bare minimum of what? a TBSpoonmm per gallon. I use more personally and I tend to not have PH issues. I did this time because I had an accumulative effect within my pots with a hard soluble material. so those were a wash almost but yes,it'll all be fine man.