1st grow - RQS Northern Light Auto

This week I'm finally starting to see some problems. Having no equipment to check PH, EC, temperature or humidity, it's normal that there are some unbalanced parameters that I don't know of... Some leaves have thin yellow marks around their edges, and some white dots appared on one specific leaf. I've been feeding her with 1L of water plus nutrients every three days, no pure water in between, and maybe this is nutrient burn? Well, let's see. I'll be away for a week, another person will feed her but won't be able to perform LST.