SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

I am in Michigan and my sprinkler systems runs off of a well with a submersible pump. Last summer my sprinklers started to lose pressure. After a few weeks they wouldn't even pop up any more. It was extremely hot all summer and we had no rain. My first assumption was the well had dried up. This spring when I tried to fire it up, the pressure was still low, and when I turned on a zone, water also came out of the heads in other zones.

After receiving much advice, the first thing we tried was removing the pump and soaking in vinegar. Didn't help.

With some help we found the timer was shot and was telling the pump to run ALL of the time unless the breaker is off.
Replaced the timer and now the pump runs appropriately, but all the zones still run at once with low pressure.

My thought is that the pump has been running nonstop since last summer, including all winter. Water froze and messed up valves, causing the current situation. Is this reasonable or is there a more likely problem? What should my next step be?
Thanks!