To tighten or not to tighten – Spokes Help

I have a 2007 Spec Rockhopper Pro and have had the rear wheel replaced when 5 spokes broke on separate rides, and then it has hand built using upgraded DT spokes, all under warranty.

Did a simple ride this afternoon playing in the mud, came back, washed the bike to find three spokes completely loose…

Should i just tighten them up, or take it back to the LBS and have them do it?

The wheel seems true, spins freely and seems ok?

If i do it myself, how tight should they be? Anything i need to know about doing it? any advise or doing them up would be great?

Straight back to the shop. Clearly a bad build.

Def back to shop. Something properly wrong there. It may be true, but is it egg shaped?