Issue and workaround:
At Sheets API, I thought that your goal can be achieved by the method of spreadsheets.values.batchUpdate. But unfortunately, it seems that in the current stage, this method is not included in gspread. So as a workaround, I would like to propose to use the method using requests module.
When your script is modified, it becomes as follows.
Modified script:
client = gspread.authorize(creds)
sh = client.open("kite")
sheetTitles = [sh.get_worksheet(0).title, sh.get_worksheet(1).title]
values = [{'range': 'A3', 'values': fin_5min}, {'range': 'D3', 'values': fin_15min}]
reqs = [[{'range': "'" + t + "'!" + v['range'], 'values': v['values']} for v in values] for t in sheetTitles]
res = requests.post(
    'https://sheets.googleapis.com/v4/spreadsheets/' + sh.id + '/values:batchUpdate',
    headers={"Authorization": "Bearer " + creds.get_access_token().access_token, "Content-Type": "application/json"}, # modified
    data=json.dumps({"data": sum(reqs, []), "valueInputOption": "USER_ENTERED"})
)
- The access token is retrieved from 
creds of client = gspread.authorize(creds). 
- In this case, the values of 
fin_5min and fin_15min are required to be 2 dimensional array. Please be careful this. 
- By the above modification, the values of 
values are put to both the 1st and 2nd sheets. 
- And, in this modified script, please add 
import requests and import json. 
Reference: