tank crack

I have an 150 gallon acrylic tank 5x2x2 been running over 2 years got it second hand. I did water change last weekend and just cleaned the front pannel today and noticed some very small look like little cracks in the middle of the tank over about a 1ft span. They just appeared out of no were...

Just got this tank from a local who needed to rehome it. Was fine on the take down and they delivered it. Was late when I tucked it in the garage for a few days. Well i took down my other tank and got this one all ready to go. On inspection, the bottom corner in the front got chipped. Thinking...