My seedlings is 5 days old sprouted from coco on the 4th of sep. Has its first true set of leaves and started the second set of leaves. This morning I noticed some purple coloring starting on the tips. I am new to growing and not sure what the problem is. A few things I researched told me it might have gotten to cold and others have told me it can possibly be a nutrient deficiency. I have had a few growers suggest adding nutrients from day one since coco has no supplements already in it. Where should I start?