High pitched noise when toilet filling

Uk1982

Hi, looking for advice. 
When we flushed our downstairs toilet we noticed a high pitched noise which continued until the cistern had filled.  A bit of Googling told us this was likely a faulty or dirty fill valve. Since accessing the cistern requires removing a siliconed shelf, we decided to try to access the cistern tomorrow. 

However, we've just realised the exact same thing happens with the upstairs toilet! Not sure how the problem can be with the fill valve if both toilets are affected? It's a new build property (6 years) and this only started happening today. Any ideas what this could be? Upstairs toilet is also boxed in behind tiles/shelf  

Thanks in advance for any suggestions , Karen. 

Mutton_Geoff

Do you have a large push button plate to flush? If it's in the centre above the pan, you can usually remove that to access the cistern. To remove the plate, you normally slide it sideways one way and it releases from a spring.

Is the water hard where you are? Limescale could be the reason both have clogged up in a similar period of time.

Uk1982

Thanks for your reply. The water here is not hard and both toilets were fine for 6 years and then both started making the noise last night. Very strange! 
Anyway, as of about an hour ago they are both back to normal. I suspect maybe there was something stuck somewhere and it has dislodged itself maybe? Who knows. But thank you anyway! Good advice for if it happens again.