18 month old suddenly upset at nursery, help!

[MumOf1plusBump]

My 18 month old started nursery back in April (4 days a week). Took a few weeks to settle in, and caught a lot of illnesses, but then seemed to love it- eating everything, having her naps, smiling at the staff, even running in the door and barely looking back to me. I turned up at various times unannounced and watched her through the window and she seemed so happy.

All of a sudden, fast forward 6 months and now she cries, clings to my neck and won't be put down, and the nursery ring me every few days to say either she has a temperature, is upset send wants to be held all the time, or isn't sleeping (her appetite is still fine). She has this persistent cough that just won't shift, and there's been a cold going round the nursery for weeks and weeks, so they're all a bit miserable.

I just don't know what to do. I hate leaving her, and although she loves the staff there, she just wants them to hold her all the time now rather than playing with her friends. Most of the time, I drop everything, take a half day or day off, and hope it will be better the next day, but it's been going on for 6 weeks now