7 month old suddenly difficult to put down for 2nd nap

[mommy2two]

7 month old, great napper, great on BW 4-hr schedule. Wakes around 7am, first nap at 9am and usually naps 1 hr 30 min or sometimes a little more. Easy to put down for this nap. Just a quick cuddle and down she goes and is asleep within 5-10 min max. 

All of the sudden she is fussy and  cries when I put her down for her afternoon nap. This nap is usually about 2-2.5 hrs after waking  up from 1st nap. She does not take a catnap. Bedtime at 6:15pm. .

Any suggestions as to why she is so upset all of the sudden and what I should do?
Thanks!

[Layla]

At 7 months, she should be able to do close to 3hrs of A time so maybe aim for something like this (the morning A time is usually less):

7am - wake
9:30-11am - morning nap
2 - 3.30pm - afternoon nap
6.30pm - bedtime

Try adding 10-15mins to her A time & also you could try waking her up from her morning nap 15mins earlier (so let her sleep 1hr15mins) so that she is tired enough for the pm nap

hth
Layla